Manufacture of fibroin salt solutions



Patented July 2, 1935 UNITED? STATES PATENT oF-ncE MANUFACTURE OFFIBRoIN SALT;

. SOLUTIONS I Herbert Malin and Wilhelm Irion, Dessau in Anhalt,Germany, trie Aktiengesellscha Main, Germany No Drawing. ApplicationFebruary In Germany ticularly when a highly valuable albuminous materialis used, which is dispersed under mild conj ditions. When highlyconcentrated aqueous salt solutions are used for the dispersion, afibroin- 1 salt" adsorption compound may even separate.

For practical use the attempt ismade, on the one hand, to preparesolutions of a fibroin content as high as possible, and on the otherhand, to keep the viscosity as low as possible without incurring therisk of degradation. According to our invention a sufiiciently highconcentration of the fibroin solution and, at the same time, a goodhomogeneity and an average viscosity of the solution are obtainedwithout a noteworthy degradation, by adding to the salt solution eitherbefore, during or after the dispersion of the fibroin, an acid amide.Suitable acid amidesare formamide, acetamide, propionamide, malonamide,succinamide, succinimide, urea or the like. The solutions of albuminoussubstance thus obtained in a dispersing salt solution are considerablyless viscous, they flow better in the ducts and'can more easily befiltered than fibroin solutions of the same concentration without thesaid additions. When no addition of an acid amide is made to the fibroinsolution there will only be obtained solutions which are scarcely fluentor not fluent at all. However, on the addition of about 5 to percent ofan acid amide to these fibroin solutions, they show a viscosity of about60 to 80 seconds measured in the ball viscosimeter (the viscosity meansthe time, a steel ball having a diameter of 3 mm. needs for fallingthrough a column of cm.

The tendency of fibroin-salt adsorption compounds to separate from thefibroin solutions tates which have already formed can even beredissolved by addition of an acid amide; for instance the saltadsorption compounds obtained in the manner described in our copendingapassignors to geneous solutions are frequently obtained, par-' heightof the solution, the latter being kept at at high ,salt concentrationsis removed; precipiplication Serial No. 531,850 filed Apr. 21, 1931 I.G. Farbenindusft, of Frankfort on the 15, 1932, See February 23,

can, after separation of the solvent, be liquefied by mixing them withan acid amide.

The following examples illustrate the invention:

EmampZeL-E-O cc. of formamide are addedto 1000 cc. of an aqueous sodiumthiocyanate solution saturated at 50 C; The solution is heated to '70C.. In the course of minute 220 grams of degurnmed silk waste (blousses)are introd'uced and dissolved within. 5 minutes, while vigorouslystirring. The solution is then cooled to 30 C. in the course of 15-20minutes and the impurities are eliminated by filtration. The solution isused, preferably after separation of the salt by dialysis, for thepreparation of spinning solutions or plastic masses- Instead of 50 cc.of'formamide, there'can be added to the salt solution other acid amides,for instance grams of urea. By working in the same manner, withoutaddition of an acid amide, a paste is obtained which does not flow.

Example 2.-A paste prepared byintroducing at about 45 C. 100 grams ofnatural silk wastes (blousses) into about 4 kilos of an aqueous solutionof NaSCN saturated at 50 C. while well kneading for about A hour, andcontaining 14 per cent. of fibroin, 54 per cent. of sodium thiocyanateand 32 per cent. of water, is mixed at ordinary temperature with 8 percent. of formamide. A liquid, homogeneous solution is obtained.

Example 3.-l000 cc. of an aqueous solution of sodium rhodanate of about65 per cent strength are mixed with about 100 cc. of formamide or 1.20grams of urea. 200 grams of silk wastes (blousses) are introduced inthis solution at a temperature of about 35 C., care being taken that thefibrous mass is uniformly wetted by the salt solution. In the course ofan hour the silk is dissolved while stirring occasionally at thebeginning of the operation and continually towards its end. It isadvantageous to let the solution stand forsome hours at about 25 C., inorder to increase its homogeneity. Hereafter the solution is filteredand dialysed, and is then fit for tic masses.

Example 4.- cc. of formamide or grams of urea are added to 1000 cc. ofan aqueous solusolution is thoroughly stirred and kneaded as soon use inthe production of artificial threads or plasthe solution is notunlimited, but will dependupon the relations of solubility. As a rulelarger quantities than 15 per cent. of acid amide will not be used. Thequantity of acid amide and the special kind of acid amide to be added inorder to obtain the best result can in each base be determined by a fewsimple comparative experiments.

What we claim is:-

1. The process of. manufacturing an aqueous fibroin-salt solution whichcomprises adding 100 grams of urea to about 1000 cc. of an aqueous so-,

lution of sodium thiocyanate saturated at C., heating this solution toabout to C., introducing in said heated solution 220 grams of sill:waste Within about minute while vigorously stirring and cooling theresulting mixture to 30 C.

2. The process of manufacturing an aqueous fibroin solution whichcomprises adding 130 grams of urea to 1000 cc. of an aqueous solution ofsodium rhodanate of about 68 per cent. strength, introducing into saidsodium. rhodanate solution about 200 grams of silk wastes at atemperature of about 25 C. and stirring the resulting mixture until ahomogeneous solution is obtained.

3. The process of manufacturing an aqueous fibroin-salt solution whichcomprises preparing a paste containing about 14 per cent. of fibroin, 54per cent. of sodium thiocyanate and 32 per cent. of water by introducingat about 45 C. grams of natural silk wastes into about 4 kilos of asolution of NaSCN saturated at 50 C., and mixing said paste at ordinarytemperature with about 8 per cent. of formamide.

4. A composition of matter comprising an aqueous fibroin-salt solutionand an acid amide.

5. A composition of matter comprising an aqueous fibroin-salt solutionand an acid amide said acid amide being present in an amount of not morethan 15 percent.

6. In the process of manufacturing aqueous fibroin-salt solutions bydissolving fibroin in an aqueous salt solution, the step which comprisesadding an acid amide to the aqueous salt solution at any stage of thepreparation of the fibroin solution.

7. In the process of manufacturing aqueous fibroin-salt solutions bydissolving fibroin in an aqueous salt solution, the step which comprisesadding an acid amide in an amount of at most 15% to the aqueous saltsolution at any stage of the preparation of the fibroin solution.

8. A composition of mattercomprising an aqueous solution of fibroin,sodium thiocyanate and urea.

9. A composition of matter comprising an aqueous solution of fibroin,sodium thiocyanate and formamide.

l HERBERT MAHN.

WILHELM IRION.

